1. Field of the Invention
The present invention relates to a light-emitting diode (LED) lamp using a LED element, particularly to a LED lamp provided with a radiation mechanism for the LED element.
2. Description of the Related Art
Recently, because of a high light-emitting efficiency and a long lifetime, LED elements are broadly utilized in various devices such as indicator devices and illumination devices. Particularly, application for a LED lamp with the LED element housed in a casing made of an insulation material such as a resin material, which can be utilized in various environments, is considered of value.
The LED element can provide a large amount of light just at power-on. However, because the LED element has a large heating value, if there is no heat radiation mechanism, the temperature of the LED element will greatly increase. For example, in case of a LED lighting installation of 0.5 W, a surface temperature of the LED element may be sometimes increased over 120° C. If the temperature of the LED element thus increases, a light-emitting efficiency of the LED element itself decreases to shorten its life in the long run. Therefore, it is absolutely necessary to take countermeasures against heat generation when the LED lighting installation uses a high output LED element to obtain a large amount of light.
A heat sink is conventionally used to suppress rise in temperature of the LED element. For example, Japanese patent publication No. 2007-035788A discloses a LED lamp unit with a heat sink arranged to keep in contact with a circuit board on which a LED element is mounted so as to radiate generated heat from the element through the heat sink.
However, if the heat sink is arranged to keep in contact with the circuit board as the LED lamp unit disclosed in Japanese patent publication No. 2007-035788A, a size of the LED lamp unit becomes big and a manufacturing cost thereof becomes higher. Also, when such LED lamp unit is attached to a ceiling as is the case with a conventional incandescent lamp, because it is necessary to keep a space for ventilation to cool the heat sink and to install an air conditioning system in the ceiling, the construction cost will become mammoth.